I am running a 750G at home.
E1 = DHCP client for WiMax (beta test) get a dynamic... I could set it up to get a static
E2 = Master/DHCP server for 192.168.0.0/24 <-natted
E3-4 are slaves to E2
E4 = ? see below.

I have a DSL modem /pppoe. I get a static via PPPoE. The dsl modem (moto 2210) can act in bridge mode or router. Any suggestions on how I should set it up? I want to have a failover in case the WiMax fails (it's not 100% yet). Should I have the mikrotik do the PPPoe ? or have the DSL modem do it, and enable the IP passthrough feature (allows me to configure a host with the public IP from the pppoe)?

I have tried this a few different ways and have not been able to get it working. Just looking for some suggestions.